USA — A fierce bushfire in northern New Mexico continues to close in on America’s leading nuclear laboratory at Los Alamos.

The sprawling Los Alamos nuclear weapons research centre has been closed for another day as firefighters battle a blaze burning across more than 200 square kilometres.

Authorities warn the fire, fanned by strong winds, could more than double in size in coming days.

Fire chief Doug Tucker says there are no guarantees on what will happen.

“I will not say that it is not going into the lab,” he said. “We’re doing our best to keep it off the laboratory.”

The laboratory, which ensures the safety and reliability of the US nuclear stockpile, is a national security research facility located in the Jemez mountains of northern New Mexico.

Air crews have already dumped water on a spot fire on the laboratory’s south-western boundary.

“All nuclear and hazardous materials, including those at the lab’s principal waste storage site known as Area G, are accounted for and protected,” authorities said on the official New Mexico Fire Information website.

“Water tanks at the lab’s wild land fire helicopter landing pad are re-filled in preparation for today’s firefighting activities,” they said about the historic lab where the atomic bomb was developed during World War II.

The laboratory’s website confirmed the facility would remain closed until at least Wednesday (local time), and that firefighters had ordered thousands to evacuate the nearby town of Los Alamos, where more than 40 per cent of the lab’s 11,800 employees live.

“Only employees on an essential-duties access list will be permitted back onto laboratory property during the closure, as notified by their line management,” Los Alamos National Lab (LANL) said.

Radioactive materials are stored at the laboratory for research purposes and the property also houses radioactive waste.